>4. If composition is not enough go through all other similar design patterns that are not based on inheritance.

IMO, that seems like too formulaic an approach without enough thinking in that step.

Also, you mention design patterns, but the classic design pattern book nicknamed GoF (Gang of Four, i.e. by Gamma, Vlissides et al), has this guideline prominently on an early page (before the main body of text):

"Prefer composition over inheritance"

, or similar words (from memory).

And that is the only sentence on that page, right in the middle, which could only have been done for great emphasis.

But you say:

3. If interfaces are not enough, use composition

And although you do say to avoid inheritance, aren't interfaces somewhat similar to inheritance, so shouldn't the same GoF guideline apply?

Asking for myself.